Home ECG Test Kit

University of PittsburghSenior Design – BioE 1160/1161

James CookCarmen HayesJoe Konwinski

April 18, 2005

Mentor: Mingui Sun, PhD

Problem Statement

Heart disease• 2nd leading cause of death

• Number 1 killer of women

Limitation of Diagnosis• In 2003, of the 700,000 Americans that

died, only 148,000 were diagnosed

• Individuals remain unaware of the symptoms of heart attack or dismiss them

Introduction

Develop a small device that can:• Cleanly amplify the electric activity of the

heart

• Save the amplified signal onto a portable memory solution

Produce a program that can:• Analyze the ECG data and give heart-risk

feedback to the user

Be Sold Over-the-Counter Be User Friendly and Safe

Purpose

Purpose is:• To assess heart risk of seemingly HEALTHY, middle to upper aged individuals

• To give a cheaper/ less demanding alternative for healthy patients

Purpose is NOT:• To replace a health professional in assessing heart

risk of ILL or HEAVY RISK individuals

Let Us Be Frank….

Market

What’s There…• Marquette MARS® PC Holter Monitoring &

Review System--$11,500

• Burdick Vision® Holter Analysis System

--$6,000

All Marketed Devices are For Use By Health Care Professionals

Market Size

Based on the 2000 Census, the population of both sexes ages 40+ was 119,386,252 (42% of population). Family history Hypertension (estimated 28 million adults) Obesity (estimated 41 million adults) Smoking (estimated 20 million adults)

Constraints

Economic• Time

• Money

Regulatory• False positive

• False negative

• Patient misuse

Project Outline

Hardware Group• Develop Miniature ECG Amplifier

• Decide Proper Electrode Placement/Management

• Research Methods on Implementing a Portable Memory Solution

Software Group• Understand the Mechanism behind ECG

diagnoses

• Develop a Computer Algorithm to Interpret Imported ECG Signal

Hardware Development

Develop a Miniature ECG Amplifier

Hardware Development

Development of Miniature ECG Amplifier

• Deciding on Chips

• Bread-Board Model

• PCB development

• Testing PCB model

Hardware Development

Deciding on chips• Size

• Power Consumption

Chip Quiescent current Supply voltage

INA332 450µA +2.7 - +5.5 V

OPA2336 20µA +2.3 - +5.5V

Hardware Development

Breadboard PCB

Hardware Development

Electrode placement• Normally has 12 leads,

each one takes a “picture” of the heart from a different aspect.

Hardware Development

Normal Recording

Hardware Development

Einthoven’s Triangle

Hardware Development

Goal: Detect P, R, S, and T waves Signal

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

40 40.5 41 41.5 42 42.5

P

R

S

T

Hardware Development

Implementing Portable Memory

Current Solution:• Microchip’s PIC18F2455

• 10-bit A/D Converter

Hardware Development

Hardware Development

Hardware Development

Heart Disease & ECG Timing

Heart block (1st,2nd,3rd degree) • Timing irregularity in PR interval

Bundle branch block• Long QRS interval

Arrhythmia• Heart rate too fast or slow (<60; >100 BPM)

Myocardial Ischemia• Depressed ST segment

Clinically, the electrocardiogram is a powerful tool in diagnosing certain types of heart disease.

MuscleContraction

Software Development

Moving median filter (n=fs) to calculate baseline

Locate areas of muscle contraction using threshold detector (±0.4V from baseline)

Find largest gap of continuous data between contractions for use in further analysis

If largest gap is smaller than 12 sec, prompt user to recollect data and to try to relax his/her body

Subtract baseline from data

Use Butterworth 2nd order lowpass (fl =15 Hz) to remove high frequency noise

Signal Conditioning

Q

P, noise

R

Q, P, noise

T

S

Software Development

K-means cluster analysis locates cluster centroids and groups data points with centroids to minimize sum of squares Heuristics based on derivatives, amplitudes, and relative locations of peaks/valleys give each cluster a label (i.e. P, Q, R, S, T)

•Need to test at least 40 “normal” patients before this step is complete

ECG Analysis

Peak-detector algorithm locates peaks/valleys in the ECG along with their amplitudes and derivatives

Software Development

User is given feedback consisting of:

Type Subtype Risk WeightHeart Block 1st degree 92% 2%

1st degree heart block is caused by…It results in…It is usually treated by…

2nd degree 10% 5%

2nd degree heart block…

3rd degree 0.2% 40%

3rd degree heart block…

…

TOTAL RISK 11%

User Feedback Calculate peak-to-peak timing and important slopes of ECG Statistical analysis calculates a percent risk of each disease and, by weighting each disease, a total risk of disease

1st degree heart block is diagnosed when the PR interval is greater than 0.2 seconds

Criteria for Success

Design of on-chest ECG hardware

Ability to detect peak-to-peak time intervals

programmatically

Completing:

Successes

Nearing completion of the computer program

Developed a miniature ECG amplifier

Verified that signal peaks can be detected with chest-mounted electrodes

Future Work

Finish computer program

Design and implement flash memory storage

Create a working prototype

Acknowledgements

Dr. Mingui Sun

Dr. Marc Simon

Drs. Hal Wrigley and Linda Baker for their generous donation

Questions?